The performance of phytoremediation has proven effective in the removal of nutrients and metals from aqueous systems. However, little information is available regarding the behavior of pesticides and their removal pathways in aquatic environments involving plant-uptake. A detailed understanding of the kinetics of pesticide removal by plants and information on compound/plant partition coefficients can lead to an effective design of the phytoremediation process for anthropogenic pesticide reduction. It was determined that the reduction rates of four organophosphorus (OP) and two organochlorine (OC) pesticides (diazinon, fenitrothion, malathion, parathion, dieldrin, hexachlorobenzene [HCB]) could be simulated by first-order reaction kinetics. The magnitude of k was dependent on the pesticide species and found within the range of 0.409 -0.580 d -1 . Analytical results obtained by mass balances suggested that differential chemical stability, including diversity of molecular structure, half-lives, and water solubility, would greatly influence the removal mechanisms and pathways of OPs and OCs in a phytoreactor (PR). In the case of OP pesticides, plant accumulation was an important pathway for the removal of fenitrothion and parathion from water, while pesticide sorption in suspended matter (SM) was an important pathway for removal of dieldrin and HCB. The magnitude of the pesticide migration factor ( pesticide P M) is a good indication of determining the tendency of pesticide movement from below-to above-ground biomass. The uncertainties related to the different phenomena involved in the laboratory phyto-experiment are also discussed.
Biochar is a product of thermal degradation of organic materials in the absence of air (pyrolysis). Slowpyrolyzed and biowaste-derived biochars show excellent adsorption properties. Studies on biochars produced from pine nut shells, sawdust, and cow dung have been carried out in Mongolia determining the technical characteristics and applying for improvement of soil quality. However, a thorough characterization of biochars is still in lack. In this study, we produced 10 biochars from animal bones and dungs, and firewoods and compared their characterization properties. Physico-chemical parameters of biochars such as moisture, ash, volatile matters, fixed carbons, pH, redox potential (pE), electrical conductivity (EC), total dissolved solids (TDS), cation exchange capacity (CEC), and base saturation were determined and SEM-EDX, FTIR, XRD, main elements, and trace metals analysis were obtained. Methylene blue and iodine absorption tests were carried out in terms of surface porosity. All biochars showed high electrical conductivity and base saturation indicating that they were rich in cations. The highest values of pH, EC, TDS, and CEC were found in biochar produced from sheep dung. Among bone chars, biochar produced from sheep spine bone showed the highest CEC. High Ca content in bone biochars resulted from the nature of the raw material. Biochars hardly contained trace metals. XRD analysis showed that the firewood biochar had amorphous, whereas the bone biochars and dungs had crystal structures. Biochars produced from animal and forestry biowastes have shown great values of adsorbent characteristics, thus the application of such biochars can simultaneously reduce waste and be an environmentally friendly valuable product.
Determining vertical variation of water quality parameters is contributed to a better understanding of the true nature of lakes. Lakes are classified into holomictic and meromictic lakes by their mixing mode; the former occurs physicochemical mixing between the surface and deep waters, while the latter layers of lake water occur unmixed for years, decades, or centuries. Lake Oigon is the only Meromictic Lake identified in Mongolia. Few Mongolian lakes have been studied in different seasons but not in the vertical directions. Therefore, we studied the vertical profile of water and sediment parameters in Lake Oigon for two years. Physico-chemical parameters in water were measured on-site, while sediment parameters were determined off-site. Salinity in lake water ranged from 21.3 to 65.9 g/L which represented mesosaline to hypersaline. In oxic, sub-oxic, and anoxic zones, the physico-chemical parameters of Lake Oigon were varied a lot in longitudinal ways lake and seasonal variation observed as well. However, most parameters were stable in the anoxic zone, regardless of seasons, indicating that no water movement was at the bottom of the lake. Layered sediments with salt indicating hardly exchange with lake water at the anoxic zone. The statistical correlation and principal component analysis between the various physico-chemical parameters of lake water and lake sediment were computed. This study provides the basic information for future research on the characteristic of the vertical profile, impact on the ecosystem, and environmental assessment for Lake Oigon.
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